1. Technical Field
This description pertains generally to treatment of carpal tunnel syndrome and more particularly to both a method and apparatus for treatment by inserting a surgical instrument with a probe into the carpal tunnel and dividing the flexor retinaculum.
2. Background Discussion
Carpal tunnel syndrome (CTS) is a disease that refers to numerous clinical signs and symptoms resulting from an increase in pressure on the median nerve within the carpal tunnel. The increased pressure often compresses the median nerve, compromising its blood flow, resulting in the pain, numbness, and tingling characteristic of this disease. At present, it is the most widespread occupational health hazard in the industrial world. Billions of dollars are spent each year in lost working time and in the diagnosis and treatment of this syndrome.
Although the underlying cause of CTS is unknown, the treatment for CTS is well established. Non-operative treatments, including splinting, anti-inflammatory medications, and cortisone injections into the carpal tunnel, are often used initially to provide temporary relief of the symptoms. When non-operative treatments fail, the most effective treatment for CTS is surgical division of the flexor retinaculum (often called transverse carpal ligament). Surgical division of the flexor retinaculum causes the divided edges of the ligament to retract; creating a decrease in pressure within the carpal tunnel and restoring normal blood flow to the median nerve, thereby relieving the signs and symptoms of CTS. While various techniques exist for releasing the flexor retinaculum, the two most commonly used are referred to as open and endoscopic carpal tunnel release.
During an open release, a longitudinal incision is made through the skin in the palm and heel of the hand and carried down through the subcutaneous fat, palmar fascia, palmar brevis muscle, and finally through the flexor retinaculum. Once the flexor retinaculum is divided, the skin overlying the divided ligament is closed with conventional sutures and the wrist is frequently splinted until the wound heals. A typical surgery requires approximately 15 minutes to 30 minutes and is performed as an outpatient procedure.
For one existing technique called endoscopic carpal tunnel release (ECTR), various surgical instruments exist to perform division of the flexor retinaculum from within the carpal tunnel. For example, U.S. Pat. Nos. 4,963,147; 4,962,770; 5,089,000; 5,306,284; 7,628,798; 7,780,690; 7,918,784; 8,523,891 and 8,523,892 describe various surgical instruments that are used for ECTR surgery.
Current ECTR techniques that divide the flexor retinaculum from within the carpal tunnel offer certain advantages over the open technique. Patients have less post-operative morbidity which is defined by: a) less post-operative pain, especially with hand use; b) less weakness of grasp and pinch; c) less need for narcotics post-operatively; and d) an earlier return to activities of daily living and gainful employment.
Although advantages of current ECTR techniques have been well documented, debate still exists over whether ECTR is as safe as open release. The main objection to ECTR is the potential for injury to the median nerve. Even though the surgeon should have a direct and clear endoscopic view of the cutting blade and flexor retinaculum, injuries to the median nerve still occur. Because the cutting blade is elevated within the carpal tunnel, it may not cut only the flexor retinaculum, but may also cut the median nerve that also traverses through the carpal tunnel. Reasons for injury to the median nerve include surgeon inexperience, anatomic anomalies, inappropriate dissection techniques, anesthetic application method, forceful insertion of the endoscopic device into the carpal tunnel, poor visibility resulting from either local anesthesia infiltrate, fogging of the endoscopic lens, or excess synovial fluid, and patient movement.
Currently, all endoscopic surgical instruments that are designed for, intended for, and cleared by the U.S. Food & Drug Administration for treating CTS are inserted into the carpal tunnel to cut the flexor retinaculum from its deep to superficial surfaces. Therefore, this risk of injury to the median nerve is inherent in each of these endoscopic surgical methods.
Accordingly, an object of the present description is a surgical method and apparatus that offers the reduced post-operative morbidity advantages associated with ECTR, but reduces the risks that are inherent with current surgical instruments that cut the flexor retinaculum from within the carpal tunnel.